class_docstr: Bag-level relation extraction dataset. Note that relation of NA should be named as 'NA'.
code: def __len__(self):
      return len(self.bag_scope)
  
imports: import torch
  import torch.utils.data
  import os, random, json, logging
  import numpy
  import sklearn.metrics
label_desc: Use image node_id 2 for calling the BagREDataset obj's underlying member method code with example usage: obj.__len__() and returns: len